Vitamin D

Vitamin D is a fat-soluble vitamin. Fat-soluble vitamins are stored in the body's fatty tissue.

Function

Vitamin D helps the body absorb calcium. Calcium and phosphate are two minerals that are essential for normal bone formation.

Throughout childhood, your body uses these minerals to produce bones. If you do not get enough calcium, or if your body does not absorb enough calcium from your diet, bone production and bone tissues may suffer.

Food Sources

The body makes vitamin D when the skin is directly exposed to the sun. That is why it is often called the "sunshine" vitamin. Most people meet at least some of their vitamin D needs this way.

Very few foods naturally contain vitamin D. As a result, many foods are fortified with vitamin D. Fortified means that vitamins have been added to the food.

Fatty fish (such as tuna, salmon, and mackerel) are among the best sources of vitamin D.

Beef liver, cheese, and egg yolks provide small amounts.

Mushrooms provide some vitamin D. The vitamin D content is also being boosted by exposure to some commercially available mushrooms to ultraviolent light.

Most milk in the United States is fortified with 400 IU vitamin D per quart. It should be noted that foods made from milk, such as cheese and ice cream, are usually not fortified.

Vitamin D is added to many breakfast cereals and to some brands of soy beverages, orange juice, yogurt, and margarine. Check the nutrition fact panel on the food label.

Supplements

It can be very hard to get enough vitamin D from food sources alone. As a result, some people may need to take a vitamin D supplement. Vitamin D found in supplements and fortified foods comes in two different forms:

Recommendations

Ten to 15 minutes of sunshine three times weekly is enough to produce the body's requirement of vitamin D. The sun needs to shine on the skin of your face, arms, back, or legs (without sunscreen). Because exposure to sunlight is a risk for skin cancer, you should use sunscreen after a few minutes in the sun.

People who do not live in sunny places may not make enough vitamin D. Skin that is exposed to sunshine indoors through a window will not produce vitamin D. Cloudy days, shade, and having dark-colored skin also cut down on the amount of vitamin D the skin makes.

Because vitamin D can come from sun, food, and supplements, the best measure of one's vitamin D status is blood levels of a form known as 25-hydroxyvitamin D. Blood levels are described either as nanograms per milliliter (ng/mL) or nanomoles per liter (nmol/L), where 0.4 ng/mL = 1 nmol/L.

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